Height-adjusting mechanisms of the aforesaid type, wherein the height of the chair seat is adjusted by rotation of the chair seat when unoccupied, with the adjusting mechanism being disengaged when the chair seat is occupied, are well known and such mechanisms are now being widely used on spindle-type office chairs. In mechanisms of this general type, the spindle is threadably engaged with a nut which can be suitably held in nonrotatable relationship relative to either the base or the chair seat so as to define adjusting and nonadjusting positions. A spring normally urges the chair seat slightly upwardly when it is unoccupied so that the nut is nonrotatably connected to the base, whereby rotation of the seat causes the spindle to threadably move through the nut and hence cause a height adjustment of the seat. Conversely, when the chair seat is occupied, the external force imposed on the chair seat overcomes the spring and moves the chair seat and spindle downwardly a limited amount so that the nut is nonrotatably engaged with the spindle, whereby swivelling or rotating the occupied chair seat does not change its height.
Examples of known height-adjusting mechanisms which are generally of the above type are disclosed by U.S. Pat. Nos. 3,870,271 and 3,991,965.
U.S. Pat. No. 4,394,001, as owned by the assignee of this application, also discloses a height-adjusting mechanism of this type. While the height-adjusting mechanism of this latter patent operates in a desirable manner, nevertheless ongoing improvements in the chair and specifically in the base assembly for the chair have also resulted in improvements with respect to the height-adjusting mechanism.
More specifically, this invention relates to a height-adjusting mechanism of the type disclosed by said U.S. Pat. No. 4,394,001 but relates to improvements with respect to the structure associated with said mechanism so as to facilitate the assembly and durability of the mechanism. The improved mechanism of this invention employs a stationary clutch member formed substantially as an elongated sleevelike housing which can be stationarily secured with respect to the pedestal by an assembly technique whereby the stationary clutch member is both axially and rotatably displaced so as to lockingly join the clutch member to the pedestal without requiring separate fasteners, whereby the assembly can hence be efficiently and easily accomplished.
Other objects and purposes of the invention will be apparent to persons familiar with mechanisms of this general type upon reading the following specification and inspecting the accompanying drawings.